Plumbing the Depths / Teams of underwater divers will soon be spending weeks hundreds of feet below the surface of Shasta Lake, working on an $80 million dam retrofit designed to save the Sacramento River's decimated salmon population

Paul McHugh, Chronicle Staff Writer

Published 4:00 am, Sunday, June 4, 1995

1995-06-04 04:00:00 PDT Redding, Shasta County -- Deep-sea divers will soon descend into the icy waters of Shasta Lake and begin fitting California's biggest dam with an $80 million set of intake gates to help save the last of the Sacramento River's once-mighty salmon runs.

Nearly 50 years after the completion of Shasta Dam -- which tamed the river for Central Valley agriculture, but took a devastating toll on salmon -- the federal government is undertaking a major retrofit to undo some of the damage.

Working hundreds of feet underwater, the divers will install 9,000 tons of steel on the dam's north face so that dam operators can carefully regulate the temperature of water released from the lake to the river, assuring cool flows when the fish need them most.

For the U.S. Bureau of Reclamation, which made its reputation building concrete monoliths such as Shasta Dam, the temperature control device marks a new mission: restoring the environment.

"We're creating new technology," said Paul Capener, the bureau's area manager. "It's the first time anyone in the world has ever tried to build this type of structure underwater."

Cool flows are most critical to the salmon in summer, when the fish spawn. At temperatures above 62 degrees Fahrenheit, salmon eggs and the young fry that emerge from them cannot survive.

Since 1987, the bureau has been holding back some water until summer so it can provide the cooler flows. But the cold water is near the bottom of the reservoir, and to release it, operators must now bypass the dam's hydroelectric turbines. The bureau calculates it has lost $32 million in electric power sales as a result.

By rerouting the cooler water through the turbines, the new temperature control device should allow healthy levels of both power generation and salmon spawning.

Engineers liken the project to erecting a 35-story steel building beneath the surface of the lake. Key jobs will be done by professional divers who will live like astronauts in a space station, eating and sleeping in a pressurized 20- foot-long tank on a barge moored in Shasta Lake.

Each day, in 12-hour shifts, they will travel via a pressurized diving bell (used like a job-site elevator) to submerged work stations hundreds of feet below.

To prepare for the job, Fletcher General Construction of Seattle, the lead contractor, has already sent a tiny remote-controlled submarine with cameras and lights down the 600-foot-high dam to examine the concrete work from decades ago.

"I've worked on dam project management for 13, 14 years," said Red McClure, Fletcher's chief inspector, "and I've got to say those guys that built this dam 50 years ago did fine work, even by today's standards."

What the dam's builders did not do, however, was make provision for the salmon.

Biologists at the U.S. Fish and Wildlife Service warned at the time that the dam, the linchpin of the sprawling Central Valley Project, could doom fish downstream. But the dam -- 6.5 million cubic yards of concrete holding back 4.5 million acre-feet of water -- was built with just one outlet to the penstocks feeding the five giant turbines.

In a normal rainfall year, when the lake is high, water funneled through the turbines is cool enough (48-56 degrees Fahrenheit) to keep spawning salmon and their eggs and fry healthy and happy.

But in the 1976-77 drought, the flaw in dam design became painfully apparent. The outlet to the turbines was just 20 feet below the surface of the drought-shriveled lake, and the water it sucked through was too hot. The temperature rose to more than 60 degrees, and countless young salmon were killed.

Commercial and sport anglers and the Sierra Club Legal Defense Fund protested vigorously. They lobbied for installation of a $1 million emergency plastic "curtain" to screen off hot surface waters from the turbine intake. But nothing was built.

"The drought losses below Shasta made us aware how terribly vulnerable salmon are to California's industrial water plumbing," said Zeke Grader of the Pacific Coast Federation of Fishermen's Associations, which represented more than 5,000 commercial salmon trollers then, and only half that number today.

The real impetus for a permanent solution came in 1990 when the federal Endangered Species Act was invoked. The winter-run chinook, which had dropped to just 500 spawners, was declared threatened. The state Water Resources Control Board then ordered the bureau to keep the river at 56 degrees or cooler.

Two years later, as part of a major Central Valley Project overhaul that would commit more water to wildlife, Congress created the mechanism to pay for a temperature control device. The Central Valley Project Improvement Act put a surcharge on water and power sales and earmarked the money for environmental restoration.

"At that point, the various aspects -- financial, biological, environmental -- came together," says Capener. "Everyone here had a reawakening in terms of what was going on. All the pieces fit."

The environmental problem became an engineer's problem. The new device had to be able to siphon up 400 tons of hurtling water every second from a point 352 feet below the dam's crest. The bureau -- the agency that built Shasta, Hoover and the other great dams of the West -- was as quick as ever to rise to the engineering challenge.

Four hundred-and-fifty truckloads of steel will be welded into a framework sheathed with panels, then lowered in sections into the lake. Divers will attach the structure to the dam with 10-foot bolts. The device will have steel shutters and intakes at four levels, so operators can draw waters of differing temperatures from various depths and direct them at will through the turbines.

The federal government is covering 75 percent of the $80 million cost, with the state picking up the rest.

The underwater work will be handled by Oceaneering Technologies of Maryland, the largest diving construction firm in the United States. The first crews are set to arrive in June, and by midsummer the divers should be working round-the-clock.

Four-man teams of divers will live for a month at a time in the pressurized chamber, breathing a carefully regulated oxygen/helium mix so they won't need to decompress and re-acclimatize every day. Leaving the chamber to work their 12-hour shifts will be like heading out for a spacewalk.

"I feel a lot of sympathy for astronauts," said diver Ken Edwards, the superintendent on the underwater job. "Once you are in the 'sat' (saturation) chamber, just a half-inch of steel separates you from the outside world. But you actually feel further away. You're many days away from getting back out."

The project's completion -- the target is fall 1996 -- will be a relief for anglers and conservationists. But they caution against euphoria.

"This certainly will help our salmon runs," said biologist Harry Rechtenwald of the state Department of Fish and Game. "For one thing, it helps make up for the 100 miles of spawning area lost behind the dam. The 50 miles of spawning area below the dam will become much more productive, and reliably so.

"But realize," said Rechtenwald, "there's still other problems these salmon face."

Among them, he said, is acid runoff from old mines, inadequate fish screens on the many diversion pipes that suck irrigation water from the river, and the giant pumps in the Sacramento-San Joaquin River Delta that grind up countless fish.

Some also see irony in the fact that the laws that helped secure long-awaited protection for the threatened salmon runs -- the Endangered Species Act and the Central Valley Project Improvement Act -- are now themselves threatened.

"It's tragic," said Sausalito fisheries consultant Bill Kier, a former state biologist. "Just as science and engineering come together to resolve a 50-year-old problem, some San Joaquin agribusiness people run off to Washington with plans to ravage the two laws that made this great solution possible."